These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Designated Hero: The audience is supposed to be cheering John on, but he does a lot of very questionably moral things. He takes an entire hospital waiting room hostage, (which leads to a patient almost dying), he makes doctors work on people at gunpoint (the gun may not have been loaded, but the doctors certainly didn't know that), and he essentially steals a heart from someone else, who will then die because they couldn't find a heart. And on top of that, he never questions his actions or feels any regret about what he's doing. Instead he keeps insisting that what he's doing is right, and chews anyone out who doesn't agree with him. Not only did this stunt waste the police's time and the taxpayer's money, but he also endangered the lives of dozens of people and most likely inspired dozens of copycats, but the audience is not supposed to think about this, because he's the protagonist.
Strawman Has a Point: At one point, the hospital administrator points out to the police that they cannot, under any circumstances, give John what he wants, or else there would be "guns in every hospital". Despite the fact that John does get exactly what he wants, because he took hostages, this is never brought up again.
Tear Jerker: Denzel's powerful performance lends itself to a couple of these, particularly when he finds out about his son's condition.
Values Dissonance: To a certain degree, between American and some foreign audiences. To those in countries that have universal healthcare, many of which consider healthcare to be a human right, the American medical system displayed in the movie (and in Real Life) can range from baffling and complicated to downright horrifying.